Added label functions and auto-padding

src/System/ProgressBar.hs

@@ -1,15 +1,28 @@
 {-# LANGUAGE NoImplicitPrelude, PackageImports, UnicodeSyntax #-}
 
-module System.ProgressBar ( progressBar ) where
+module System.ProgressBar
+    ( -- * Progress bars
+      progressBar
+    , mkProgressBar
+      -- * Labels
+    , Label
+    , noLabel
+    , percentage
+    , exact
+    ) where
 
 import "base" Control.Monad ( when )
+import "base" Data.Bool     ( otherwise )
 import "base" Data.Function ( ($) )
-import "base" Data.List     ( genericReplicate )
+import "base" Data.Int      ( Int )
+import "base" Data.List     ( (++), null, genericLength, genericReplicate )
+import "base" Data.Ord      ( max )
 import "base" Data.Ratio    ( (%) )
 import "base" Data.String   ( String )
 import "base" Prelude       ( (-), round )
 import "base" System.IO     ( IO, putStr, putChar )
 import "base" Text.Printf   ( printf )
+import "base" Text.Show     ( show )
 import "base-unicode-symbols" Data.Eq.Unicode ( (≢) )
 import "base-unicode-symbols" Prelude.Unicode ( ℤ, ℚ, (⋅) )
 
@@ -19,22 +32,53 @@ import "base-unicode-symbols" Prelude.Unicode ( ℤ, ℚ, (⋅) )
 -- Erases the current line! (by outputting '\r') Does not print a
 -- newline '\n'. Subsequent invocations will overwrite the previous
 -- output.
-progressBar ∷ ℤ -- ^ Width in characters.
-            → ℚ -- ^ Current progress.
+progressBar ∷ Label -- ^ Prefixed label.
+            → Label -- ^ Postfixed label.
+            → ℤ     -- ^ Total progress bar width in characters.
+            → ℤ     -- ^ Amount of work completed.
+            → ℤ     -- ^ Total amount of work.
             → IO ()
-progressBar width fraction = do
+progressBar mkPreLabel mkPostLabel width todo done = do
     putChar '\r'
-    putStr $ progressBarString width fraction
+    putStr $ mkProgressBar mkPreLabel mkPostLabel width todo done
 
-progressBarString ∷ ℤ → ℚ → String
-progressBarString width fraction =
-    printf "%3i%% [%s%s]"
-           percentage
+mkProgressBar ∷ Label
+              → Label
+              → ℤ
+              → ℤ
+              → ℤ
+              → String
+mkProgressBar mkPreLabel mkPostLabel width todo done =
+    printf "%s%s[%s%s]%s%s"
+           preLabel
+           (pad preLabel)
            (genericReplicate completed '=')
            (genericReplicate remaining '.')
+           (pad postLabel)
+           postLabel
   where
-    percentage ∷ ℤ
-    percentage = round $ fraction ⋅ 100
-    completed = round $ fraction ⋅ (width % 1)
-    remaining = width - completed
+    fraction = todo % done
 
+    effectiveWidth = max 0 $ width - 2 - genericLength preLabel - genericLength postLabel
+
+    completed = min effectiveWidth $ round $ fraction ⋅ (effectiveWidth % 1)
+    remaining = effectiveWidth - completed
+
+    preLabel  = mkPreLabel  todo done
+    postLabel = mkPostLabel todo done
+
+    pad ∷ String → String
+    pad s | null s    = ""
+          | otherwise = " "
+
+
+type Label = ℤ → ℤ → String
+
+noLabel ∷ Label
+noLabel _ _ = ""
+
+percentage ∷ Label
+percentage done todo = printf "%3i%%" (round (done % todo ⋅ 100) ∷ ℤ)
+
+exact ∷ Label
+exact done todo = show done ++ "/" ++ show todo